1. Field of the Invention
The present invention relates to injection syringes, devices and modules, of the type for single use, especially but not exclusively for the field of dentistry.
2. Description of Related Art
Such syringes are known from manufacturers of these materials, practitioners and patients and generally comprise a body provided with a needle at a first end of the former, the needle comprising an external portion extending outside the body and an internal portion extending inside the body, the needle forming thus an end external to the body and an end internal to the body, means for grasping the body of the syringe, at a second end of the latter opposite the first end, a mobile injection rod, a detachable cartridge containing a product to be injected, disposed inside the body between the internal end of the needle and the second end of the body in an inoperative position, this cartridge being capable of moving from the inoperative position towards the first end of the body under the pressure of the injection rod, during an injection.
The devices mentioned above are made up of the syringes described below, thus intended to function in conventional manner in co-operation with a cartridge pre-filled with a product to be injected, but are marketed without this cartridge in order to allow the practitioner to introduce into it the cartridge of his choice, depending on his needs.
The modules also mentioned above are made up of a portion of the devices described above, which can be marketed without the grasping means and without the injection rod, the latter then being constituted by detachable and reusable grasping means and rod, which the user can have available, only the module (and the cartridge) being in this case for single use and disposed of after use.
Such syringes, devices and modules function perfectly. However, as is known in the field of dentistry especially, the practitioner who has to carry out an injection of anaesthetic products for example, must be assured that the external end of the syringe does not open into a blood vessel of the oral cavity. For this, the practice consists in operating slight suction by means of the injection syringe in order to check that blood does not come to color the product to be injected, if necessary.
This operation, carried out when the needle has penetrated the flesh, necessitates a delicate and hardly practical maneuver with the devices of prior art, by precisely measured traction applied to the injection rod whilst keeping the body immobile, which traction must not be too strong in order to avoid the possible introduction of too large a quantity of blood if necessary, but sufficient to make it possible to ensure verification in a certain manner.
There is known, especially through the French application no. 2,696,096, a syringe making it possible to improve the suction operation by introducing a xe2x80x9cdamperxe2x80x9d for the displacement of the rod, as it were. This application teaches a syringe comprising a rod fitted at one end with a head complementary in cross-section to the internal cross-section of the cartridge, said head being intended to rest on the mobile plug of the cartridge to permit the expulsion of the product outside the latter via the injection needle, this head being capable of sliding on the internal walls of the cartridge and presenting an escape conduit connecting the volume delimited between the head and the plug to the exterior of the cartridge, this escape conduit having a significant loss of load.
Thus the air imprisoned in a first period of time in the above volume is expelled via the escape conduit, in such a way as to permit the head to come into contact with the plug. In a second period of time, the user, via weak traction exercised on the rod, is going to move the head over a short distance in the direction of the position before use; the plug still adhering momentarily to the internal wall of the cartridge, a partial vacuum is then going to be created between the head and the plug, in such a way as to constrain the latter to leave its position and to come into contact with the head again. Displacing the plug in the direction of its position before use is thus going to generate a slight suction phenomenon, sufficient in any case to permit the possible introduction of several drops of blood into the cartridge if need be.
This device, which functions perfectly and significantly improves the prior devices necessitating a complex maneuver of the rod by combined rotation and traction, nevertheless requires the practitioner to exercise traction in order to create a suction phenomenon.
Document WO 94/16752 is known which relates to a self-injection device having a tubular sleeve in which is axially arranged a cartridge closed at its front end by a membrane and at its rear end by a piston. An injection needle is fitted sliding axially in the cartridge. A tubular actuating cap, secured against removal, is guided sliding on the rear end of the sleeve and makes it possible to actuate the device via a rod which acts on the piston and extends from the bottom of the cap into the sleeve. This device comprises, between the membrane of the sleeve and a shutter, placed in the sleeve and carrying the needle, a protective cap intended to keep a portion of the needle in sterile conditions, and a spacer spring, the function of which is to keep the cartridge at a distance from the internal end of the needle in order to avoid accidental piercing of the membrane, whilst allowing its compression to permit the device to function. In an alternative manner, the functions of the protecting cap and the spacer spring can be combined in the same part.
The object of the present invention is to propose injection syringes, devices and modules of the type for single use, making it possible to overcome the disadvantages of known syringes, devices and modules, and making it possible for, the practitioner to carry out the suction operation without having to apply traction to the injection rod, whilst proposing systems which are simple in conception and practical to use.
Another object of the present invention is to propose injection syringes, devices and modules of the type for single use, making possible minimal sterile packaging, and advantageously without wrapping up the syringe body.
Another object of the present invention is to supply injection syringes, devices and modules of the type for single use which permit, thanks to the suction without traction, a reduction in the sterile packaging of the proposed injection syringes, devices and modules.
Another object of the present invention is to propose injection syringes, devices and modules of the type for single use, at modest costs compatible in particular with the intention of single use of these products.
Another object of the present invention is to propose injection syringes, devices and modules of the type for single use, providing for the user and for third parties, excellent security against accidental pricking with the injection needle.
To this end, the present invention consists of an injection syringe of the type for single use, especially for the field of dentistry, comprising:
syringe body fitted with a needle at a first end of the former, said needle comprising an external portion extending outside said body and an internal portion extending inside said body, said needle forming an end external to said body and an end internal to said body,
means for grasping said syringe body, at a second end of the latter, opposite said first end,
a mobile injection rod,
a cartridge containing a product to be injected, disposed inside said body between said internal end of the needle and said second end of the body in an inoperative position, said, cartridge being capable of moving from the inoperative position towards said first end, of the body under the pressure of the injection rod elastic means for automatically returning the cartridge towards said inoperative position when the pressure on said injection rod is released, in order to cause a depression in said cartridge, characterized in that said elastic means are disposed inside said body between the first end of the letter and said cartridge, and in that said elastic means are formed by a flexible tubular envelope surrounding said internal portion of the needle.
Thanks to a return induced by the elasticity of, an appropriate material, the elastic means, as defined above, allow the user to be spared any traction force in order to carry out the suction operation, necessary to check that the needle is not placed in a blood vessel. Thus the practitioner only has to apply force in a single direction when carrying out an injection, whether this be for the injection itself of the product, or for the suction operation. Indeed, when the practitioner wants to check if the external end of the needle has penetrated a blood vessel, he only has to release the pressure exercised on the injection rod, the elastic means then returning the cartridge towards the inoperative pre-injection position, thus causing a depression in the cartridge itself, therefore sucking up the blood via the end of the needle engaged in a blood vessel, if need be,
According to another advantageous characteristic, said elastic means are guided by said internal portion of the needle.
According to another advantageous characteristic, the syringe according to the invention to comprises detachable means of covering at least the external portion of the needle, these means being intended to be removed before the injection, and said flexible tubular envelope covers said internal portion of the needle in such a way as to define a sterile space enclosing the needle, inside the flexible tubular envelope and the covering means.
This characteristic makes it possible to avoid sterile packaging of the complete syringe and to confine the needle alone in a sterile environment, which further reduces the costs of the sterile packaging. The double function played by the tubular envelope in this case will be noted.
According to another advantageous characteristic, the syringe according to the invention comprises a protective sheath moveable along said syringe body, between two extreme positions, one of which permits covering said external portion of the needle and the other the disengagement of the external portion of the needle.
This characteristic provides excellent security for the practitioner and third parties against accidental pricking with the soiled needle after injection. Indeed, once the injection has been carried out, the practitioner places the sheath in a position covering the external portion of the needle, thus avoiding anybody accidentally pricking himself whilst manipulating the syringe.
The invention will be better understood, and other characteristics and advantages will appear in reading the following description of an embodiment of a syringe, a device and a module according to the invention, accompanied by the attached drawings, these examples being given by way of illustration and without any restrictive interpretation of the invention being able to be taken from them.